Martin Linge Extended Well Test: Field-Development Decision

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 159275, ’Martin Linge Extended Well Test: Key Acquisition for the Field- Development Decision,’ by Jean-Luc Boutaud de la Combe, Total S.A.; Steinar Kvinnsland, Total EP UK; and Remy Marmier and Jenny Morante-Gout, Total EP Norway, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 8-10 October. The paper has not been peer reviewed. The Martin Linge field was discovered in the 1970s but was never developed because of uncertainties. The complex structural settings of the Brent reservoirs were the main issue: Transmissibility through numerous faults has a direct effect on the number and type of development wells required for appropriate drainage. In 2009–10, Total drilled an appraisal well to reduce the risk of this challenging development. The primary objective was to evaluate the dynamic connectivity through faults at the Upper Brent level of Martin Linge East with an extended well test (EWT). The well-completion system used acoustic wireless downhole gauges and a communication system to transfer pressure data up to the subsea wellhead and then to shore by a communication link. This made it possible to obtain extended pressure-buildup (BU) data after the rig had left. Introduction The Martin Linge field is in the Norwegian sector of the Northern Viking graben, along the border between the UK and Norway in approximately 120-m water depth. The Greater Martin Linge area consists of several fault blocks in which high-pressure gas/condensate discoveries have been made in the Upper Jurassic Upper Brent formation. From seismic evaluation, the Martin Linge East structure appears to be the largest structure in the Greater Martin Linge area. The Martin Linge East structure was penetrated by two wells in 1976 and 1978, encountering gas in the Brent at approximately 3800 m subsea. The structural interpretation, although heavily faulted, suggested Upper Brent juxtaposition everywhere within the field. However, data from the two wells suggested that at least one barrier exists between the wells, preventing lateral connectivity. The seismic imaging of the structure is relatively poor because of a gas cloud above the base Cretaceous unconformity, and significant risk exists of additional faults being masked on the seismic. Consequently, the main uncertainty for the field was linked to fault behavior and lateral connectivity. In 2009–10, Total drilled an appraisal well to assess two undrilled compartments on the structure, collect static data, and carry out a dynamic test in one of the compartments to evaluate developing the field. Martin Linge Appraisal Strategy The Greater Martin Linge area comprises several strongly faulted and segmented structural traps, with gas accumulations in the Jurassic Brent group. This highly faulted area is at the southern extremity of the Statfjord/Brent/Alwyn structural trend, lying on a structural nose on the western flank of the Viking graben. The area is on the eastern edge of the East Shetland basin on the western footwall of the North Viking graben. A significant improvement of the structural interpretation and field understanding came with several seismic acquisitions in 2003 and 2005 and the associated processing projects. The current seismic structural interpretation is based on a complete depth-imaging project, including all available streamer and ocean- bottom-cable data on the license. This work identified Martin Linge East as the biggest structure within the Greater Martin Linge area and a logical target for further development appraisal.